This invention deals with apparatus for performing chemical reactions, and, more particularly, with self-contained reaction apparatus for performing a sequential set of chemical reactions, and monitoring the final results.
In several types of chemical and medical test procedures, a liquid such as a body fluid must be reacted with individual reactants in a sequence of related but separate chemical reactions, and then the final product analyzed. Traditionally, such procedures have been performed by placing the fluid into a reaction tube or the like, adding the remaining reactants for the first reaction, and permitting the first reaction to proceed to completion. The further reactants for the second reaction are added, and the second reaction is permitted to proceed to completion. This stepwise operation can be repeated as many times as necessary, until a final reaction product is obtained for analysis.
This approach requires considerable technical expertise by the person performing the test, since reactants must be carefully measured and added at the correct times. If any of the reactants are perishable or deteriorate with time, the person performing the testing must exercise a critical judgment as to whether the reactants are suitable for performing the test at that time. Because these types of expertise must usually be specially taught, it is not always possible to use such testing procedures at rural or remote locations, as the necessary trained personnel, reactants, and facilities are not available.
Certain types of testing procedures do not lend themselves to such wet chemical techniques. One example is a test procedure wherein the final reaction product is analyzed by a luminescence reaction. In this type of procedure, the amount of a final product is indicated by the amount of light produced in a light producing reaction, one of whose reactants is the final product of one or more prior reactions. In certain types of luminescent reactions, the light is produced within a few seconds after the reactants are mixed together. If the traditional wet chemical procedure is used, the luminescent reactants must be mixed with the final reaction product and placed within a photometer or camera that measures the light, and the light detection initiated, within no more than about two seconds, or much of the resulting light is not measured and is lost. As is apparent, attempting to add precise amounts of reactants and perform the light measurement under such time pressures is difficult, and often leads to a mistake that requires the test to be repeated. Sometimes the mistake cannot be readily detected, and erroneous results are reported. Better techniques are therefore required to utilize sequential procedures where a final product is detected with a luminescent reaction.
An example of such a testing procedure is the detection of harmful bacteria in the urine of persons by luminescence, termed a bacteriuria test. For many years, the presence of bacteria in urine has been determined by culturing experiments which take at least 24 to 48 hours to perform and may yield inaccurate results. Culturing procedures are also costly, and often cannot be accomplished at remote locations.
More recently, a testing procedure has been developed whereby the presence of bacteriuria is detected more quickly, utilizing luminescent tagging of reaction products. In such a procedure, bacteria in urine are detected by releasing the chemical adenosine triphosphate, also termed ATP, from the bacteria. The available ATP reacts with bioluminescent reactants to produce light, and the amount of light measured indicates the concentration of bacteria initially present. ATP can also be present from other, non-bacterial sources, and any such extraneous ATP is first removed from the system, before releasing the bacterial ATP. Thus, there is a first chemical reaction whereby the extraneous ATP present from all non-bacterial sources is eliminated, a second, separate chemical reaction whereby the bacterial ATP is released into solution, and finally a third reaction of the light producing reactants with the released bacterial ATP. The second and third reactions can be performed simultaneously, but the first reaction must be completed before the bacterial ATP is released. This test is direct and reliable, and relatively inexpensive.
The luminescent test for bacteriuria can be performed by conventional wet chemical procedures such as previously described, but in this form suffers from many of the drawbacks discussed earlier, and in addition must be performed in darkness so that the production of light can be measured. An automatic luminometer testing apparatus has also been developed, which permits all of the reactions to be conducted within a single analytical luminescence apparatus, and yields a quantitative measure of the bacteriuria present in the urine of a patient. This approach has significantly advanced the art of bacteriuria testing.
The luminometer testing apparatus, however, costs several thousand dollars to purchase. Its use in some circumstances, such as rural and undeveloped areas, is therefore limited. The chemicals used in the luminometer are perishable. Additionally, in many instances the use of the luminometer provides much more information than is necessary. For example, in most cases urine samples yield negative bacteriuria results. The quantitative analysis capability of the luminometer is not required as to those negative results. Furthermore, it is generally observed that positively testing patients are usually heavily positive, and there are few cases of borderline results where the urine specimen contains a bacteriuria count near the arbitrarily defined dividing line between positive and negative results. The proper treatment is often identical for all positively testing persons. That is, in the majority of instances a simple qualitative determination of negative or positive bacteriuria count in a specimen is sufficient for screening purposes, and in many cases it is sufficient for all diagnostic purposes. In the event that further quantitative study is required, then the luminometer at a central location could be used more efficiently than for general screening studies.
There is therefore a need for an apparatus and test protocol for performing qualitative or semi-quantitative tests for bacteriuria by the luminescent analysis procedure. The apparatus must permit controlled sequential chemical reactions, and specifically must permit removal of non-bacterial ATP prior to the release of bacterial ATP for luminescent detection. The apparatus should be sufficiently simple that it can be used by technicians with little training, should serve to minimize errors due to chemical deterioration or technician error, and should be inexpensive so that tests can be performed economically. The present invention fulfills this need, and further provides related advantages.